Leather-dressing process



Patented Mar. 18, 1930 UNITED STATES OTTO LUDWIG STEVEN, OF BERLIN, GERMANY LEATHER-DRESSING PROCESS NoDfawing. Application filed June 30, 1928, Serial No. 289,624, and. in Germany July 22, 1927.

My invention relates to the art of dressing leather by way of asupplementary loading process and more particularly to a process in which sulphite extracts, that is the waste sulphite lye. obtained from the digesters of the sulphite cellulose process or synthetic tanning agents, are employed for subjecting tanned leather to such supplementary or finishing treatment.

In the art of dressing tanned leather by way of the said supplementary .or finishing treatment it is customary to treat the same subsequently with glue or casein solutions and the like for the purpose of fixing the tanning substances incorporated with the leather by the said supplementary or finishing treatment or in other, words, reducing the proportion of water-soluble constituents of the said substances. The lignosulphonic acids contained in the sulphite extracts or lyes and in the synthetic tanning a ents, however, are not at all or not comp etely bound or precipitated by substances such as glue, casein and the like and, therefore,

exclusively with tanning agents of the stated kinds for the finishing purpose ought not to be subjected to such a treatment with glue, casein or the like.

vide a method of treating leather with cer tain particular substances which will act to bind or precipitate ligno-sulphonic acids and synthetic tanning agents thoroughly and fix ploy, according to the present invention and in connection with the usual-supplementary or finishing loading 0 eration, water-soluble salts or compounds e f carbo-cyelicbases' as a fixing means.

Another object of my invention is to provide a method in which afterthe leather has The chief object of my invention to pro.-

the same in the leather. To this end I emfacture, leather which is characterized by a minimized loss of weight upon washing and in which the tanning substances are fixed while the substances which are not of tanning nature, have been removed or, in other Words, which is nearly devoid of the substances of non-tanning nature.

My invention is preferably racticable in connection with leather which as been subjected to a tanning treatment by means of vegetable tanning agents alone or a mixed treatment by means of vegetable and mineral tanning materials. The com ounds I employ as above stated for the xing purpose are, for instance, the salts and h drates of anilin, benzidin,-naphthylamin an in carrying out my invention practically 'I soak the leather in a solution of the mentioned salts or hydrates either before or during or after the said finishing or supplementary treatment. i

I shall now proceed to describe a few examples illustrating the invention more in detail. leather which has been treated partially or E sample 1.100 kg. of leather which have been subjected to a tanning treatment by means ,of a ve etable tanmng extract or liquor with or without an admixture of waste sulphite cellulose l e or extract, are immediately thereupon ulled or worked in a re volving hot-air vat or tub containing 15 kg. of a mixture of two parts by weight of waste sulphite lye or extract and one part of a vegetable tanning extract; The temperature 1s ept at 359 C. and the working or fullinf continues until all extract'has-been absorbe When this condition is reached a solution of 1 kg. of anilin chloro-hydrate in IOlitres of water is addedto the leather in the vat and .l the fulling operation is repeated and contin- 9p ued until the leather is dry, whereupon the leather is greased in the usual manner, for instance by means of an emulsion of 1 k of Turkey-red-oil and 1 kg. of fishroil in 5 litres of water.

Example 2.- kg. of leather which has been subjected to a tanning treatment as in Example 1 are first fulled in the revolving vat with a solution of 1 kg; of anilin chlorohydrate in 10 litres of water until the leather I100 is dry whereupon the material under treatment 1s subjected to a fulling operation in the hot vat at a temperature of about 35 C. and

in the presence of 15 kg. of a mixture of litres of sulphite cellulose lye of 6 B. (specific gravity 1.045), for two to three hours. After that the exhausted tanning liquid is drawn ofi'and 100 litres of a 0.25 per cent solution of anilin chloro-hydrate of a temperature of about 60 C. are poured into the vat and allowed to act for about 30 minutes. Subsequently the'liquor or bath is to be neutralized with the aid of litmus paper as an indicator, by slowly adding thereto calcined soda, approximately 100 gram thereof being necessary for the purpose. Ultimately 3 kg. of a suitable greasing oil are added in order to be absorbed which is usually attained within minutes.

Example 4.l00 kg. of leather previously tanned by means of vegetable tanning extracts are subjected to a supplemental oading treatment in a mixture of 10 kg. fluid quebracho extract containing 33 per .cent of tanning substance and 10 kg. of the so-called tanning substance F manufactured by the J. G. F arbenindustrie and universally known in all countries. Subsequently the leather is subjected to a fullingoperation in a revolving greasing vat containing a solution of 0.2 kg. of B-naphthyamin chloro-hydrate in 10 litres of water, until all liquid is absorbed by the leather. The final oiling of the leather is carried out in the usual manner.

Example 5.Leather previously tanned as described in any of the foregoing examples and subjected to a supplemental loading operation by means of sulphite cellulose extract or by means of the latter in conjunction with any synthetic tanning materials, is fixed in the same way as set forth in any of the Examples 1 to 4 and subsequently washed out in the vat with water of a temperature of 30 C. After havingbeen dried as usual the leather is oiled in the customary way.

In a process carried out in accordance with the present invention the ligno-sulphonic acids of the cellulose sulphite extract or lye which is scarcely capable of sucking in water and less pervious to water than leather manufactured according to the old art. A further advantage of the present invention resides in the fact that leather made in accordance with my improved process has not those objectionable properties, particularly the bad smell which are associated with the treatment of leather with sulphite cellulose lye as a loading agent in the supplemental or finishing step. Furthermore leather made according to the present invention does not crack and its colour does not deepen as otherwise is the case when glue, casein and the like are employed for fixing purposes.

- Though I have described with great particularity of detail certain specific ways of carrying out my invention, yet it is not to be understood therefrom that the invention is limited to such particular performances, and I, therefore, hold myself at liberty to make such departures therefrom as fairly fall within the true scope and spirit of my invention.

hat I claim is 1. In the 'art' of tanning hides the step which comprises filling the leather with a substance which can be fixed therein by a water soluble salt of a carbocyclic amine, and the step of causing the so-filled leather to absorb from an aqueous solution thereof the amount of a salt of a carbocyclic amine almost suflicient 'to fix the said filling agent therein.

2. In the art of tanning hides the step which comprises filling the leather with a substance which can be fixed therein by a water soluble salt of a carbocyclic amine, and the step of causing the so-filled leather to absorb from an aqueous solution thereof the amount of a salt of a carbocyclic amine almost sufficient to fix the said filling agent therein, and the further step of then washing out the water soluble non-tans from the so-filled and fixed leather.

3. A leather containing the reaction products between a filling substance capable of being fixed by a water soluble salt of a carbocyclic amine, and said salt being substantially free from non-tanning substances.

In testimony whereof I aflix my signature.

OTTO LUDWIG STEVEN.

and the tanning substances of the synthetic I tanning extracts or materials are converted into non-hygroscopic compounds and this is the reason why an improved leather will be produced according to the present mvention, 

